**1. Introduction**

Since China's reform and opening up, with the acceleration of industrialization, largescale land resources have been continuously developed. Urban construction land is also faced with environmental problems, such as occupying ecological space, air pollution, water pollution, and ecological imbalance. How to coordinate social and economic development with ecological and environmental protection has become the core issue of sustainable development research in China. At the 18th National Congress of the Communist Party, the five-sphere integrated strategy of giving prominence to ecological progress was put forward from an overall and strategic perspective. At the same time, it pointed out that optimizing the spatial development pattern of the national territory should be taken as the primary measure of ecological civilization construction, so as to promote intensive and efficient production space, livable and appropriate living space, and beautiful (picturesque scenery) ecological space [1–3].The "Production–Living–Ecological" space (production space, living space, and ecological space, PLES), as the main body of the spatial pattern

**Citation:** Lin, G.; Jiang, D.; Fu, J.; Zhao, Y. A Review on the Overall Optimization of Production–Living –Ecological Space: Theoretical Basis and Conceptual Framework. *Land* **2022**, *11*, 345. https://doi.org/ 10.3390/land11030345

Academic Editors: Benedetto Rugani and Hossein Azadi

Received: 31 December 2021 Accepted: 24 February 2022 Published: 25 February 2022

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optimization, has become an important foundation for the planning and implementation of functional zones at all levels, the establishment of the spatial planning system, and the improvement of the system for the development and protection of territorial space. At the third Plenary Session of the 18th CPC Central Committee in November 2013, a number of major issues concerning comprehensively deepening reform were discussed in depth, and the Decision of the CPC Central Committee on Some Major Issues Concerning Comprehensively Deepening Reform was adopted. The decision calls for accelerating the construction of an ecological civilization system, establishing a spatial planning system, delimiting the limits of space development control, and implementing use control. In May 2019, the Opinions of the CPC Central Committee and the State Council on Establishing a Territorial Space Planning System and Supervising its Implementation identified the main objectives of territorial space planning, which included that "By 2035, China will comprehensively modernize its governance system and capacity of land and space, and basically form the national space pattern featuring intensive and efficient production space, livable and appropriate living space, beautiful ecological space, secure, harmonious, competitive and sustainable."

PLES basically covers the space activity scope of human social life, and is the basic carrier of human economic and social development. The three are independent and inter-related, with a symbiotic integration and restriction effect. The synergistic effect of "Production–Living–Ecological" (PLE) will be greater than the sum of its parts [4]. Coordinating the spatial function and land-use structure under the linkage of PLES; promoting the coordinated development of the quantity structure and spatial layout of PLES; and taking into account factors such as population distribution, economic development, territorial space utilization, and ecological and environmental protection to improve the layout of PLES in a scientific and reasonable way is the key measure to promote the building of a beautiful China, and accelerate the transformation of the way of production and living to "green" under the overall layout of the national ecological civilization construction [5]. It is also an important means to promote high-quality development and quality of life with the center of people, which is both necessary in reality, and urgent of the times. Since the report of the 18th CPC National Congress first clarified the development requirements of PLES from the height of national strategy, PLES has become the practice subject and research focus of territorial space planning and urban planning [6]. At present, the relevant theoretical research and local practice of PLES are still in the exploratory stage [7]. Related research and work mostly focused on the formulation of policies and management methods, or the evaluation and analysis of a single "space", such as demarcating the red line for basic farmland protection, the red line for ecological protection, and the boundary of urban development. These studies lack comprehensive and integrated studies of PLES in the whole domain, and lack systematic and comprehensive technical ideas and application practices of overall optimization of PLES.

Based on the classification, identification, evaluation, and optimization of PLES as the theme, through filtering and sorting the published literature since 2012 (the 18th CPC National Congress), the optimization theory, method, and practice of PLES was combed systematically, which oriented the national spatial planning. In order to provide theoretical support for the optimization of territorial space development, protection, and planning, this study also tries to put forward the development direction of the overall optimization of PLES in the future.
